Assessment of the psychiatric status or psychosocial functioning of young children poses difficult problems for research and clinical evaluation. Different data sources often yield different evaluations. In the longitudinal study of children and affectively ill and well parents, we have utilized a multisource and multimethod approach in assessing the children. Of particular interest are comparisons of (1) mothers' and fathers' reports, (2) parents' and childrens' interviews, and (3) psychiatric interview data and direct observations of behavior. What are the best combinations of data sources for evaluating the psychosocial functioning of young children? With children, five years and younger, evaluations by psychiatrists (based on a structured play session and a structured interview) and by mothers (Child Behavior Check List) show low overlap in assessments of anxiety, disruptive behavior, and depressive qualities. In middle to late childhood, psychiatrists are more likely than mothers to see depressive qualities in children. In judging overall problematic behavior in children, psychiatrist and affectively ill mothers are in somewhat better agreement than psychiatrist and normal control mothers.